Drive device and power module

Abstract

Provided is a drive device capable of suppressing an overshoot of source potential of a switching element even when a resistance value of a shunt resistance for detecting current of the switching element is large. A drive device driving a lower side switching element of an inverter circuit includes a drive circuit generating a drive signal being input to a gate of the lower side switching element and an overcurrent detection circuit detecting overcurrent flowing in the lower side switching element. The overcurrent detection circuit detects overcurrent based on voltage occurring in a shunt resistance connected to a source of the lower side switching element. The drive circuit applies potential of a connection node of the source of the lower side switching element and the shunt resistance as reference potential, and generates a drive signal of the lower side switching element.

What is claimed is: 
     
       1. A drive device configured to generate a drive signal for driving a gate of a switching element, comprising:
 an overcurrent detection circuit configured to detect overcurrent flowing in the switching element based on a voltage occurring in a shunt resistance connected to a source of the switching element; and 
 at least one drive circuit configured to directly apply a shifted potential of a connection node of the source of the switching element and the shunt resistance as a reference potential and configured to generate the drive signal for driving the gate of the switching element. 
 
     
     
       2. The drive device according to  claim 1 , wherein
 the at least one drive circuit is configured to generate the drive signal for turning off the switching element, thereby protecting the switching element, when the overcurrent detection circuit detects the overcurrent. 
 
     
     
       3. The drive device according to  claim 1 , wherein
 the overcurrent detection circuit is configured to compare a comparison reference voltage obtained by shifting a level of reference potential of the shunt resistance and a monitor voltage obtained by shifting a level of the potential of the connection node of the switching element and the shunt resistance, and is configured to determine that the overcurrent occurs when the monitor voltage exceeds the comparison reference voltage. 
 
     
     
       4. The drive device according to  claim 3 , wherein
 the overcurrent detection circuit includes a power source circuit, 
 the overcurrent detection circuit includes a first voltage-dividing circuit configured to generate the comparison reference voltage by dividing a voltage between the reference potential of the shunt resistance and an output potential of the power source circuit, and 
 the overcurrent detection circuit includes a second voltage-dividing circuit configured to generate the monitor voltage by dividing a voltage between the potential of the connection node of the switching element and the shunt resistance and the output potential of the power source circuit. 
 
     
     
       5. The drive device according to  claim 4 , wherein
 the first voltage-dividing circuit is a ladder resistance configured to change a node from which the comparison reference voltage is taken out. 
 
     
     
       6. The drive device according to  claim 4 , wherein
 the second voltage-dividing circuit is a ladder resistance configured to change a node from which the monitor voltage is taken out. 
 
     
     
       7. The drive device according to  claim 4 , wherein
 the power source circuit includes a trimming mechanism configured to adjust the output potential. 
 
     
     
       8. The drive device according to  claim 1 , wherein
 a capacitive element is connected in parallel to the shunt resistance. 
 
     
     
       9. The drive device according to  claim 1 , wherein
 a filter circuit configured to remove a noise is included in a path for supplying the potential of the connection node of the switching element and the shunt resistance to the at least one drive circuit as the reference potential for the drive signal for driving the gate of the switching element. 
 
     
     
       10. A power module, comprising:
 three inverter circuits each including a series circuit of an upper side switching element and a lower side switching element; 
 a high-voltage side drive device configured to drive the upper side switching element of each of the three inverter circuits; and 
 a low-voltage side drive device configured to drive the lower side switching element of each of the three inverter circuits, wherein 
 the low-voltage side drive device is the drive device according to  claim 1 , and 
 the low-voltage side drive device includes three of the at least one drive circuits, each of the three of the at least one drive circuits being configured to generate a drive signal of the lower side switching element of a corresponding one of the three inverter circuits. 
 
     
     
       11. The drive device according to  claim 1 , wherein
 a reference node configured to provide the shifted potential of the connection node to the drive circuit as the reference potential is directly connected to the at least one drive circuit and directly connected to the overcurrent detection circuit.